U.S. patent application number 12/351518 was filed with the patent office on 2010-07-15 for cutter profile helping in stability and steerability.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Thorsten SCHWEFE.
Application Number | 20100175929 12/351518 |
Document ID | / |
Family ID | 42317125 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100175929 |
Kind Code |
A1 |
SCHWEFE; Thorsten |
July 15, 2010 |
CUTTER PROFILE HELPING IN STABILITY AND STEERABILITY
Abstract
An improved drill bit comprises a bit body, a plurality of
blades disposed on the bit body, a first plurality of cutting
elements disposed on the blades, such that the first plurality of
cutting elements define a first cutter profile, and a second
plurality of cutting elements disposed on the blades, such that the
second plurality of cutting elements define a second cutter profile
offset from the first cutter profile. The first plurality of
cutting elements may, or may not, be greater in number than the
second plurality of cutting elements. The cutting elements of the
first plurality may, or may not, be greater in size than the
cutting elements of the second plurality. The second cutter profile
may be offset inwardly or outwardly from the first cutter profile.
The second cutter profile may run along a cone section, a nose
section, and/or a shoulder section of the bit.
Inventors: |
SCHWEFE; Thorsten; (Spring,
TX) |
Correspondence
Address: |
LOCKE LORD BISSELL & LIDDELL LLP;ATTN: IP DOCKETING
600 TRAVIS, SUITE 3400
HOUSTON
TX
77002-3095
US
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
42317125 |
Appl. No.: |
12/351518 |
Filed: |
January 9, 2009 |
Current U.S.
Class: |
175/431 |
Current CPC
Class: |
E21B 10/43 20130101;
E21B 10/55 20130101; E21B 10/567 20130101 |
Class at
Publication: |
175/431 |
International
Class: |
E21B 10/00 20060101
E21B010/00 |
Claims
1. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of blades disposed on
the bit body; a first plurality of cutting elements disposed on the
blades, such that the first plurality of cutting elements define a
first cutter profile; and a second plurality of cutting elements
disposed on the blades, such that the second plurality of cutting
elements define a second cutter profile offset from the first
cutter profile, wherein each profile is exclusive for at least a
portion of each blade.
2. The drill bit as set forth in claim 1, wherein the first
plurality of cutting elements are greater in number than the second
plurality of cutting elements.
3. The drill bit as set forth in claim 1, wherein the cutting
elements of the first plurality are greater in size than the
cutting elements of the second plurality.
4. The drill bit as set forth in claim 1, wherein the second cutter
profile is offset inwardly from the first cutter profile.
5. The drill bit as set forth in claim 1, wherein the second cutter
profile is offset outwardly from the first cutter profile.
6. The drill bit as set forth in claim 1, wherein the second cutter
profile runs along a cone section.
7. The drill bit as set forth in claim 6, wherein the first cutter
profile runs along a gage section, a shoulder section, and a nose
section, but not the cone section.
8. The drill bit as set forth in claim 1, wherein the second cutter
profile runs along a nose section.
9. The drill bit as set forth in claim 8, wherein the first cutter
profile runs along a gage section, a shoulder section, and a cone
section, but not the nose section.
10. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of blades disposed on
the bit body; a first plurality of cutting elements disposed on the
blades, such that the first plurality of cutting elements define a
first cutter profile; and a second plurality of cutting elements
disposed on the blades, such that the second plurality of cutting
elements are fewer in number than the first plurality of cutting
elements and define a second cutter profile offset from the first
cutter profile, wherein the first cutter profile runs along a gage
section and a shoulder section, and wherein the second cutter
profile exclusively runs along at least a portion of at least one
of a nose section and a cone section.
11. The drill bit as set forth in claim 10, wherein the second
cutter profile is offset inwardly from the first cutter
profile.
12. The drill bit as set forth in claim 10, wherein the second
cutter profile is offset outwardly from the first cutter
profile.
13. The drill bit as set forth in claim 1, wherein the second
cutter profile is offset from the first cutter profile by at least
0.15 inches.
14. The drill bit as set forth in claim 1, wherein the second
cutter profile is offset from the first cutter profile between
twenty-five and seventy-five percent of an average diameter of the
first plurality of cutting elements.
15. The drill bit as set forth in claim 1, wherein the second
cutter profile is offset from the first cutter profile between
twenty-five and seventy-five percent of an average diameter of the
second plurality of cutting elements.
16. The drill bit as set forth in claim 1, wherein the second
cutter profile is offset from the first cutter profile between
twenty-five and seventy-five percent of an average diameter of the
cutting elements.
17. The drill bit as set forth in claim 10, wherein the second
cutter profile is offset from the first cutter profile by at least
0.15 inches.
18. The drill bit as set forth in claim 10, wherein the second
cutter profile is offset from the first cutter profile between
twenty-five and seventy-five percent of an average diameter of the
first plurality of cutting elements.
19. The drill bit as set forth in claim 10, wherein the second
cutter profile is offset from the first cutter profile between
twenty-five and seventy-five percent of an average diameter of the
second plurality of cutting elements.
20. The drill bit as set forth in claim 10, wherein the second
cutter profile is offset from the first cutter profile between
twenty-five and seventy-five percent of an average diameter of the
cutting elements.
21. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of blades disposed on
the bit body; a first plurality of cutting elements disposed on the
blades, such that the first plurality of cutting elements define a
first cutter profile; and a second plurality of cutting elements
disposed on the blades, such that the second plurality of cutting
elements define a second cutter profile offset from the first
cutter profile, wherein the second cutter profile is offset from
the first cutter profile by at least 0.15 inches.
22. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of blades disposed on
the bit body; a first plurality of cutting elements disposed on the
blades, such that the first plurality of cutting elements define a
first cutter profile; and a second plurality of cutting elements
disposed on the blades, such that the second plurality of cutting
elements define a second cutter profile offset from the first
cutter profile, wherein the second cutter profile is offset from
the first cutter profile between twenty-five and seventy-five
percent of an average diameter of the first plurality of cutting
elements.
23. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of blades disposed on
the bit body; a first plurality of cutting elements disposed on the
blades, such that the first plurality of cutting elements define a
first cutter profile; and a second plurality of cutting elements
disposed on the blades, such that the second plurality of cutting
elements define a second cutter profile offset from the first
cutter profile, wherein the second cutter profile is offset from
the first cutter profile between twenty-five and seventy-five
percent of an average diameter of the second plurality of cutting
elements.
24. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of blades disposed on
the bit body; a first plurality of cutting elements disposed on the
blades, such that the first plurality of cutting elements define a
first cutter profile; and a second plurality of cutting elements
disposed on the blades, such that the second plurality of cutting
elements define a second cutter profile offset from the first
cutter profile, wherein the second cutter profile is offset from
the first cutter profile between twenty-five and seventy-five
percent of an average diameter of the cutting elements.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO APPENDIX
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The inventions disclosed and taught herein relate generally
to drill bits, such as for drilling into earth formations; and more
specifically relate to cutter profiles for such drill bits that
improve performance especially in the areas of stability and
steerability.
[0006] 2. Description of the Related Art
[0007] U.S. Pat. No. 4,440,247 teaches a "blade-type rotary drill
bit having radially divergent cutting blades arranged in two arrays
and equipped with cutting blanks having upset cutting surfaces
formed of an abrasive material such as diamond or the like. The
blades in one array cut to the center of the bit to provide a
conically shaped core volume and the blades of the second array
terminate short of the axis of the bit to define a somewhat larger
core volume. The bit is equipped with discharge ports and baffles
whereby drilling fluid issuing from the discharge ports moves
downwardly and then inwardly to the center of the bit. The cutting
blanks located on the second array of blades cut in a common set of
tracks which are at least partially different from and compliment
the tracks cut by the cutting blanks on the blade of the first
array."
[0008] U.S. Pat. No. 4,593,777 teaches a "drill bit comprises a bit
body having an operating end face. A plurality of self-sharpening
cutters are mounted in the bit body and extend through the
operating end face. The cutters have cutting faces adapted to
engage an earth formation and cut the earth formation to a desired
three-dimensional profile. The cutting faces define surfaces have
back rake angles which decrease with distance from the profile. The
individual cutting faces may be inwardly concave in a plane
parallel to the intended direction of motion of the cutter in use.
Each of the cutting members has a stud portion disposed in a
respective recess in the bit body and defining the inner end of the
cutting member, the cutting face being generally adjacent the outer
end and having an outer cutting edge. The centerline of the stud
portion is rearwardly inclined, from the outer end to the inner
end, with respect to the direction of movement in use, taken at the
midpoint of the cutting edge, at a first angle from 80.degree. to
30.degree. inclusive. The cutting face is oriented such that the
tangent to the cutting face at the midpoint of the cutting edge and
in the center plane of the cutting member is disposed at a second
angle, for 18.degree. to 75.degree. inclusive, with respect to the
centerline of the stud portion."
[0009] U.S. Pat. No. 4,932,484 teaches a "whirl resistant drill bit
is disclosed for use in rotary drilling. The drill bit includes a
generally cylindrical bit body with a plurality of cutting elements
extending out from a lower end surface. The cutter elements are
grouped in sets such that a first set of cutters are disposed at
substantially an equal radius from a center of the bit body to
create a groove in the material being drilled. A second set of
cutters is connected to the lower end surface with each cutter
therein in overlapping radial relationship with each other and
extending a maximum distance from the lower end surface less than
that of the first set of cutters. At least one cutter of the second
set is in overlapping radial relationship with at least one of the
cutters within the first set of cutters. This cutter arrangement
causes the drill bit to cut grooves within the formation material
that tends to prevent destructive bit whirl. Further, adjustments
can be made to vary the back rake angle and side rake angle to
prevent bit whirl."
[0010] U.S. Pat. No. 5,033,560 teaches an "earth boring bit having
a body provided with a shank having a tubular bore and a head along
the opposite end of said body having flow passages communicating
with the bore, the head having face portions including a center end
face portion, a nose portion, a shoulder portion, and a gage
portion along the maximum diameter of the bit, and cutting elements
mounted over said face portions having cutting faces oriented in
the direction of rotation of the drill bit, the areas of the
cutting faces of the cutting elements ranging from a maximum at the
center face portion to a minimum at the gage portion of the bit.
The cutters may be individually mounted, mounted in groups,
arranged in random patterns, and arranged in a variety of other
patterns, including radial longitudinal rows circumferentially
spaced around the bit face."
[0011] U.S. Pat. No. 5,238,075 teaches a "fixed cutter drill bit
includes a plurality of angularly spaced radial wings each with a
row of cutting elements mounted thereon and protruding from the bit
for drilling through formation material. On a first of the wings, a
first row of the cutting elements has alternately larger and
smaller area cutting faces at spaced selected radial positions
relative to the center of the bit. Similarly, a second row of
cutting elements is mounted on a second of the wings at
substantially the same radial positions but with the radial
positions of the larger and smaller cutting faces reversed over
those on the first wing. A third wing includes a third row of
cutting elements with cutting faces of intermediate area located at
each of the selected radial positions. The combination of different
sizes of cutting elements at each radial position defines a set
having a profile with the intermediate and smaller cutting elements
located entirely within the larger cutting element. The profiles of
the larger cutting elements of adjacent sets overlap each other
without substantial overlapping of the profiles of any of the other
cutting elements."
[0012] U.S. Pat. No. 5,549,171 teaches a "fixed cutter drill bit
includes sets of cutter elements mounted on the bit face. Each set
includes at least two cutters mounted on different blades at
generally the same radial position with reset to the bit axis but
having differing degrees of backrake. The cutter elements of a set
may be mounted having their cutting faces out-of-profile, such that
certain elements in the set are exposed to the formation material
to a greater extent than other cutter elements in the same set. The
cutter elements in a set may have cutting faces and profiles that
are identical, or they may vary in size or shape or both. The bit
exhibits increased stability and provides substantial improvement
in ROP without requiting excessive WOB."
[0013] U.S. Pat. No. 5,551,522 teaches a "fixed cutter drill bit
includes a cutting structure having radially-spaced sets of cutter
elements. The cutter element sets preferably overlap in rotated
profile and include at least one low profile cutter element and at
least two high profile elements. The low profile element is mounted
so as to have a relatively low exposure height. The high profile
elements are mounted at exposure heights that are greater than the
exposure height of the low profile element, and are radially spaced
from the low profile element on the bit face. The high profile
elements may be mounted at the same radial position but at
differing exposure heights, or may be mounted at the same exposure
heights but at different radial positions relative to the bit axis.
Providing this arrangement of low and high profile cutter elements
tends to increase the bit's ability to resist vibration and
provides an aggressive cutting structure, even after significant
wear has occurred."
[0014] U.S. Pat. No. 5,607,025 teaches a "fixed cutter drill bit
includes cutter elements mounted in sets on the bit face. A cutter
element set includes at least three cutters with cutting faces
having at least two different curvatures. The cutter elements of
the set are mounted on various blades of the bit such that, in
rotated profile, the cutting profile of a larger and a smaller
cutter element overlap, and such that the smaller cutter element is
flanked by larger sized cutters. The bit exhibits increased
stability, before and after wear has occurred. The large cutters
provide for efficient shearing while the smaller cutters may
provide prefracturing in certain formations."
[0015] U.S. Pat. No. 5,582,261 teaches a "fixed cutter drill bit
includes sets of cutter elements mounted on the bit face, each set
including at least two cutters that are mounted at generally the
same radial position with respect to the bit axis. The cutter
elements of a set are positioned on different blades of the bit and
are mounted having their cutting faces are out-of-profile, such
that certain elements in the set are exposed to the formation
material to a greater extent than other cutter elements in the same
set. The cutter elements in a set may have equal diameters or may
vary in size. The bit exhibits increased stability or vibration
resistance, and drills initially as a `light-set` bit and later as
a `heavy-set` bit."
[0016] U.S. Pat. No. 7,000,715 teaches a "superabrasive
cutter-equipped rotary drag bit especially suitable for directional
drilling in subterranean formations is provided. The bit may employ
PDC cutters in an engineered cutter placement profile exhibiting
optimal aggressiveness in relation to where the cutters are
positioned along the profile of the bit extending from a cone
region laterally, or radially, outward toward a gage region
therefore. The engineered cutter placement profile may include
cutters exhibiting differing degrees of aggressiveness positioned
in order to maximize rate-of-penetration and minimize torque-on-bit
while maintaining side cutting capability and steerability."
[0017] The inventions disclosed and taught herein are directed to
drill bits with improved cutter profiles for enhancing performance
and specifically stability and steerability.
BRIEF SUMMARY OF THE INVENTION
[0018] Applicants have created an improved drill bit, such as for
drilling into an earth formation. The drill bit preferably
comprises a bit body, a plurality of blades disposed on the bit
body, a first plurality of cutting elements disposed on the blades,
such that the first plurality of cutting elements define a first
cutter profile, and a second plurality of cutting elements disposed
on the blades, such that the second plurality of cutting elements
define a second cutter profile offset from the first cutter
profile. The first plurality of cutting elements may, or may not,
be greater in number than the second plurality of cutting elements.
The cutting elements of the first plurality may, or may not, be
greater in size than the cutting elements of the second plurality.
The second cutter profile may be offset inwardly or outwardly from
the first cutter profile. The second cutter profile may run along a
cone section, a nose section, and/or a shoulder section of the
drill bit.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0019] FIG. 1 illustrates a perspective view of an exemplary drill
bit incorporating cutting elements and embodying certain aspects of
the present inventions;
[0020] FIG. 2 is an enlarged perspective view of an exemplary
cutting element embodying certain aspects of the present
inventions;
[0021] FIG. 3 is a partial elevation view of a blade of a drill bit
according to certain aspects of the present inventions;
[0022] FIG. 4 is an elevation view of a cutter profile of a drill
bit according to certain aspects of the present inventions;
[0023] FIG. 5 is a elevation view of multiple cutter profiles of a
drill bit according to certain aspects of the present
inventions;
[0024] FIG. 6 is another elevation view of multiple cutter profiles
of a drill bit according to certain aspects of the present
inventions; and
[0025] FIG. 7 is another elevation view of multiple cutter profiles
of a drill bit according to certain aspects of the present
inventions.
DETAILED DESCRIPTION
[0026] The Figures described above and the written description of
specific structures and functions below are not presented to limit
the scope of what Applicants have invented or the scope of the
appended claims. Rather, the Figures and written description are
provided to teach any person skilled in the art to make and use the
inventions for which patent protection is sought. Those skilled in
the art will appreciate that not all features of a commercial
embodiment of the inventions are described or shown for the sake of
clarity and understanding. Persons of skill in this art will also
appreciate that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's ultimate goal for the commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill in this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
[0027] Applicants have created an improved drill bit, such as for
drilling into an earth formation. The drill bit preferably
comprises a bit body, a plurality of blades disposed on the bit
body, a first plurality of cutting elements disposed on the blades,
such that the first plurality of cutting elements define a first
cutter profile, and a second plurality of cutting elements disposed
on the blades, such that the second plurality of cutting elements
define a second cutter profile offset from the first cutter
profile. The first plurality of cutting elements may, or may not,
be greater in number than the second plurality of cutting elements.
The cutting elements of the first plurality may, or may not, be
greater in size than the cutting elements of the second plurality.
The second cutter profile may be offset inwardly or outwardly from
the first cutter profile. The second cutter profile may run along a
cone section, a nose section, and/or a shoulder section of the
drill bit.
[0028] FIG. 1 is an illustration of a drill bit 10 that includes a
bit body 12 having a conventional pin end 14 to provide a threaded
connection to a conventional jointed tubular drill string
rotationally and longitudinally driven by a drilling rig.
Alternatively, the drill bit 10 may be connected in a manner known
within the art to a bottomhole assembly which, in turn, is
connected to a tubular drill string or to an essentially continuous
coil of tubing. Such bottomhole assemblies may include a downhole
motor to rotate the drill bit 10 in addition to, or in lieu of,
being rotated by a rotary table or top drive located at the surface
or on an offshore platform (not shown within the drawings).
Furthermore, the conventional pin end 14 may optionally be replaced
with various alternative connection structures known within the
art. Thus, the drill bit 10 may readily be adapted to a wide
variety of mechanisms and structures used for drilling subterranean
formations.
[0029] The drill bit 10, and select components thereof, are
preferably similar to those disclosed in U.S. Pat. No. 7,048,081,
which is incorporated herein by specific reference. In any case,
the drill bit 10 preferably includes a plurality of blades 16 each
having a forward facing surface, or face 18. The drill bit 10 may
have anywhere from two to sixteen blades 16. While in one preferred
embodiment, the face 18 is substantially flat, it may be concave
and/or convex.
[0030] The drill bit 10 also preferably includes a row of cutters,
or cutting elements, 20 secured to the blades 16. The drill bit 10
also preferably includes a plurality of nozzles 22 to distribute
drilling fluid to cool and lubricate the drill bit 10 and remove
cuttings. As customary in the art, gage 24 is the maximum diameter
which the drill bit 10 is to have about its periphery. The gage 24
will thus determine the minimum diameter of the resulting bore hole
that the drill bit 10 will produce when placed into service. The
gage of a small drill bit may be as small as a few centimeters and
the gage of an extremely large drill bit may approach a meter, or
more. Between each blade 16, the drill bit 10 preferably has fluid
slots, or passages, 26 into with the drilling fluid is fed by the
nozzles 22.
[0031] An exemplary cutting element 20 of the present invention, as
shown in FIG. 2, includes a super-abrasive cutting table 28 of
circular, rectangular or other polygon, oval, truncated circular,
triangular, or other suitable cross-section. The super-abrasive
table 28, exhibiting a circular cross-section and an overall
cylindrical configuration, or shape, is suitable for a wide variety
of drill bits and drilling applications. The super-abrasive table
28 of the cutting element 20 is preferably formed with a
conglomerated super-abrasive material, such as a polycrystalline
diamond compact (PDC), with an exposed cutting face 30. The cutting
face 30 will typically have a top 30A and a side 30B with the
peripheral junction thereof serving as the cutting region of the
cutting face 30 and more precisely a cutting edge 30C of the
cutting face 30, which is usually the first portion of the cutting
face 30 to contact and thus initially "cut" the formation as the
drill bit 10 retaining the cutting element 20 progressively drills
a bore hole. The cutting edge 30C may be a relatively sharp
approximately ninety-degree edge, or may be beveled or rounded. The
super-abrasive table 28 will also typically have a primary
underside, or attachment, interface joined during the sintering of
the diamond, or super-abrasive, layer forming the super-abrasive
table 28 to a supporting substrate 32 typically formed of a hard
and relatively tough material such as a cemented tungsten carbide
or other carbide. The substrate 32 may be preformed in a desired
shape such that a volume of particulate diamond material may be
formed into a polycrystalline cutting, or super-abrasive, table 28
thereon and simultaneously strongly bonded to the substrate 32
during high pressure high temperature (HPHT) sintering techniques
practiced within the art. Alternatively, the substrate 32 may be
formed of steel, or other strong material with an abrasion
resistance less than that of tungsten carbide and/or the earth
formation being drilled. In still other embodiments, the substrate
32 may comprise a relatively thin tungsten carbide layer backed by
a steel body.
[0032] In any case, the substrate 32 may be cylindrical, conical,
tapered, and/or rectangular in over-all shape, as well as,
circular, rectangular or other polygon, oval, truncated circular,
and/or triangular, in cross-section. A unitary cutting element 20
will thus be provided that may then be secured to the drill bit 10
by brazing or other techniques known within the art, such as
gluing, press fitting, and/or using a stud mounting technique.
[0033] In accordance with the present invention, the super-abrasive
table 28 preferably comprises a heterogeneous conglomerate type of
PDC layer or diamond matrix in which at least two different nominal
sizes and wear characteristics of super-abrasive particles, such as
diamonds of differing grains, or sizes, are included to ultimately
develop a rough, or rough cut, cutting face 30, particularly with
respect to the cutting face side 30B and most particularly with
respect to the cutting edge 30C. In one embodiment, larger diamonds
may range upwards of approximately 600 .mu.m, with a preferred
range of approximately 100 .mu.m to approximately 600 .mu.m, and
smaller diamonds, or super-abrasive particles, may preferably range
from about 15 .mu.m to about 100 .mu.m. In another embodiment,
larger diamonds may range upwards of approximately 500 .mu.m, with
a preferred range of approximately 100 .mu.m to approximately 250
.mu.m, and smaller diamonds, or super-abrasive particles, may
preferably range from about 15 .mu.m to about 40 .mu.m.
[0034] The specific grit size of larger diamonds, the specific grit
size of smaller diamonds, the thickness of the cutting face 30 of
the super-abrasive table 28, the amount and type of sintering
agent, as well as the respective large and small diamond volume
fractions, may be adjusted to optimize the cutter 20 for cutting
particular formations exhibiting particular hardness and particular
abrasiveness characteristics. The relative, desirable particle size
relationship of larger diamonds and smaller diamonds may be
characterized as a tradeoff between strength and cutter
aggressiveness. On the one hand, the desirability of the
super-abrasive table 28 holding on to the larger particles during
drilling would dictate a relatively smaller difference in average
particle size between the smaller and larger diamonds. On the other
hand, the desirability of providing a rough cutting surface would
dictate a relatively larger difference in average particle size
between the smaller and larger diamonds. Furthermore, the
immediately preceding factors may be adjusted to optimize the
cutter 20 for the average rotational speed at which the cutting
element 20 will engage the formation as well as for the magnitude
of normal force and torque to which each cutter 20 will be
subjected while in service as a result of the rotational speeds and
the amount of weight, or longitudinal force, likely to be placed on
the drill bit 10 during drilling.
[0035] While PDC cutters, such as those discussed above, are used
in a preferred embodiment, other cutters may be used alternatively
and/or additionally. For example, cutters made of thermally stable
polycrystalline (TSP) diamond, in triangular, pin, and/or circular
configuration, cubic boron nitride (CBN), and/or other
superabrasive materials may be used. In some embodiments, even
simple carbide cutters may be used.
[0036] The blades 16 of modern drill bits often have three or more
sections that serve related and overlapping functions.
Specifically, referring to FIG. 3, each blade 16 preferably has a
cone section, nose section, a shoulder section, and a gage section.
The cone section of each blade is preferably a substantially linear
section extending from near a center-line of the drill bit 10
outward. Because the cone section is nearest the center-line of the
drill bit 10, the cone section does not experience as much, or as
fast, movement relative to the earth formation. The slope and
length of the cone section commonly influences stability of the bit
10.
[0037] The nose represents the lowest point on a drill bit.
Therefore, the nose cutter is typically the leading most cutter.
The nose section is roughly defined by a nose radius. A larger nose
radius provides more area to place cutters in the nose section. The
nose section begins where the cone section ends, where the
curvature of the blade 16 begins, and extends to the shoulder
section. More specifically, the nose section extends where the
blade profile tangentially matches a circle formed by the nose
radius. The nose section experiences much more, and more rapid,
relative movement than does the cone section. Additionally, the
nose section typically takes more weight than the other sections.
As such, the nose section experiences much more wear than does the
cone section. The nose section is also a more significant
contributor to rate of penetration and drilling efficiency than the
cone section.
[0038] The shoulder section begins where the blade profile departs
from the nose radius and continues outwardly on each blade 16 to a
point where a slope of the blade is essentially completely
vertical, at the gage section. The shoulder section experiences
much more, and more rapid, relative movement than does the cone
section. Additionally, the shoulder section typically takes the
brunt of abuse from dynamic dysfunction, such as bit whirl. As
such, the shoulder section experiences much more wear than does the
cone section. The shoulder section is also a more significant
contributor to rate of penetration and drilling efficiency than the
cone section.
[0039] The gage section begins where the shoulder section ends.
More specifically, the gage section begins where the slope of the
blade is predominantly vertical. The gage section continues
outwardly to an outer perimeter or the gage 24 of the drill bit 10.
The gage section experiences the most, and most rapid, relative
movement with respect to the earth formation. However, at least
partially because of the high, substantially vertical, slope of the
blade 16 in the gage section, the gage section does not typically
experience as much wear as does the shoulder section and/or the
nose section. The gage section does, however, typically experience
more wear than the cone section.
[0040] Referring also to FIG. 4, the row of cutters 20 are
preferably spaced along a curved outer edge of the face 18 of each
blade 16, forming a first, or primary, curved cutter, or cutting,
profile, or layout, 34. The cutter profile 34, as shown, is a
composite of the cutting elements 20 on each blade 16, as the bit
10 rotates through the earth formation. In other words, the cutter
profile 34 comprises each of the cutting elements 20 super-imposed
as if each cutting elements 20 were rotated into a single plane of
a blade 16 extending from bit body 12. In many cases, the profile
34 generally follows the shape of the blades 16.
[0041] According to certain aspects of the present invention,
however, there may be more than one cutter profile 34. For example,
referring also to FIG. 5, the bit 10 may have a first, or primary,
cutter profile 34, and a second, or secondary, cutter profile 36
offset from the first cutter profile 34. As shown in FIG. 5, FIG.
6, and FIG. 7, the second cutter profile 36 may be offset inwardly
or outwardly from the first cutter profile 34. The second cutter
profile 36 may be offset from the first cutter profile 34 between
0.020 inches and 0.2 inches, or more. In one preferred embodiment,
the second cutter profile 36 is offset from the first cutter
profile 34 approximately 0.15 inches. The second cutter profile 36
may be offset from the first cutter profile 34 by some percentage
of the cutter diameter. For example, the second cutter profile 36
may be offset from the first cutter profile 34 by between
twenty-five and seventy-five percent of the diameter of the cutting
elements 20, of the first profile 34, the second profile 36, or an
average thereof. In one embodiment, the second cutter profile 36 is
offset from the first cutter profile 34 by approximately 50% of the
diameter of the cutting elements 20, of the first profile 34.
[0042] The second cutter profile 36 may be located along the cone,
nose, and/or shoulder sections. More specifically, the secondary
cutter profile 36 may span more than one adjacent section, such as
the cone and nose sections, and/or may span two or more
non-adjacent sections, such as the cone and shoulder sections, with
the first cutter profile 34 being located along the remaining
sections.
[0043] The second cutter profile 36 preferably comprises a
plurality of the cutting elements 20. The second cutter profile 36
may, or may not, comprise all of the cutting elements 20 in the
affected section, or sections. For example, the second cutter
profile 36 may comprise between five and one hundred percent of the
cutting elements 20 in the affected section or sections. In one
embodiment, the second cutter profile 36 comprises approximately
all of the cutters 20 in the cone section. In another embodiment,
the second cutter profile 36 comprises approximately 75% of the
cutters 20 in the nose section. In another embodiment, the second
cutter profile 36 comprises approximately 50% of the cutters 20 in
the shoulder section.
[0044] In any case, as also shown in FIG. 5, FIG. 6, and FIG. 7,
the second cutter profile 36 may comprise fewer cutting elements 20
than the first cutter profile 34. Alternatively, the second cutter
profile 36 may comprise roughly the same number, or more, cutting
elements 20 than the first cutter profile 34. In one embodiment,
the first cutter profile 34 comprises approximately forty cutting
elements, while the second cutter profile comprises approximately
ten cutting elements. The second cutter profile 36 may comprise a
percentage of the cutting elements 20, such as ten, fifteen, or
twenty percent. Alternatively, the second cutter profile 36 may
comprise a fraction of the cutting elements 20, such as
one-quarter, one-third, or one-half.
[0045] In one embodiment, the cutting elements 20 in each profile
34, 36 are oriented similarly, other than the offset. In other
embodiments, the cutting elements 20 in the second profile 36
utilize a different back rake and/or side rake. For example, in one
embodiment, the cutting elements 20 in the second profile 36
utilize more back rake than the cutting elements 20 in the first
profile 34.
[0046] Other and further embodiments utilizing one or more aspects
of the inventions described above can be devised without departing
from the spirit of Applicant's invention. For example, the cutting
elements 20 in each profile may be the identical. Alternatively,
the cutting elements 20 may be differently sized, shaped, and/or
constructed. Additionally, or alternatively, the drill bit 10 may
include three or more cutter profiles, with each being inwardly or
outwardly and located in any of the blade sections. Further, the
various methods and embodiments of the present invention can be
included in combination with each other to produce variations of
the disclosed methods and embodiments. Discussion of singular
elements can include plural elements and vice-versa.
[0047] The inventions have been described in the context of
preferred and other embodiments and not every embodiment of the
invention has been described. Obvious modifications and alterations
to the described embodiments are available to those of ordinary
skill in the art. The disclosed and undisclosed embodiments are not
intended to limit or restrict the scope or applicability of the
invention conceived of by the Applicants, but rather, in conformity
with the patent laws, Applicants intend to fully protect all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
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